Tom,
I dont see redo_size REDUCED when TEMP_UNDO_ENABLED=true.
Is that Temp undo is not supported in multitenant Architecture?
(looks like the parameter works at SYSTEM level but not at SESSION level)
http://docs.oracle.com/cd/E16655_01/server.121/e17633/logical.htm#CNCPT89227 rajesh@PDB1> create global temporary table gtt
2 on commit delete rows
3 as
4 select * from all_objects
5 where 1 = 0;
Table created.
rajesh@PDB1>
rajesh@PDB1> alter session set temp_undo_enabled=false;
Session altered.
rajesh@PDB1>
rajesh@PDB1> set autotrace traceonly statistics
rajesh@PDB1> insert into gtt
2 select * from all_objects ;
73812 rows created.
Statistics
----------------------------------------------------------
482804 redo size
73812 rows processed
rajesh@PDB1>
rajesh@PDB1> update gtt
2 set object_name = lower(object_name);
73812 rows updated.
Statistics
----------------------------------------------------------
7162396 redo size
73812 rows processed
rajesh@PDB1> set autotrace off
rajesh@PDB1>
rajesh@PDB1> commit;
Commit complete.
rajesh@PDB1>
rajesh@PDB1>
rajesh@PDB1> alter session set temp_undo_enabled=True;
Session altered.
rajesh@PDB1> set autotrace traceonly statistics
rajesh@PDB1> insert into gtt
2 select * from all_objects ;
73812 rows created.
Statistics
----------------------------------------------------------
482848 redo size
73812 rows processed
rajesh@PDB1>
rajesh@PDB1>
rajesh@PDB1> update gtt
2 set object_name = lower(object_name);
73812 rows updated.
Statistics
----------------------------------------------------------
5648620 redo size
73812 rows processed
rajesh@PDB1> set autotrace off;
rajesh@PDB1> commit;
Commit complete.
rajesh@PDB1>
current implementation restriction.
temp undo is supported (you have reported that yourself above???? you started with "is it true" but then immediately said "it works like this"), but not as a session settable capability.